UPDATE 表A A
SET A.字段1 = 值1,
A.字段2 = 值2,
A.字段3 = 值3
WHERE EXISTS (SELECT 1
FROM 表B B
WHERE A.关联字段 = B.关联字段
AND A.字段 = 值
AND B.字段 = 值
)
update b set b.字段A =(select max(a.字段A) from 表1 a where a.id =b.id)
from 表2 b where b.id in (select id from 表1);
--或者
update b set b.字段A=a.字段A from 表1 a ,表2 b where a.id=b.id